Inhibitory activity of salicylic acid on lipoxygenase-dependent lipid peroxidation.
BACKGROUND
Since iron is essential for lipoxygenase activity and salicylic acid (SA) can interact with the metal, possible lipoxygenase inhibition by SA was investigated.


METHODS
Kinetic spectrophotometric evaluation of enzymatic lipid peroxidation catalyzed by soybean lipoxygenase (SLO), rabbit reticulocyte 15-lipoxygenase (RR15-LOX), porcine leukocyte 12-lipoxygenase (PL12-LOX) and human recombinant 5-lipoxygenase (HR5-LOX) with and without SA.


RESULTS
SA inhibited linoleic, arachidonic and docosahexaenoic acid or human lipoprotein peroxidation catalyzed by SLO with IC50 of, respectively, 107, 153, 47 and 108 microM. Using the same substrates, SA inhibited RR15-LOX with IC50 of, respectively, 49, 63, 27 and 51 microM. Further, arachidonic acid peroxidation catalyzed by PL12-LOX and HR5-LOX was inhibited by SA with IC50 of 101 and 168 microM, respectively. Enzymatic inhibition was complete, reversible and non-competitive. Conceivably due to its lower hydrophobicity, aspirin was less effective, indicating acetylation-independent enzyme inhibition. SA and aspirin were ineffective peroxyl radical scavengers but readily reduced Fe3+, i.e. FeCl3, to Fe2+, suggesting their capacity to reduce Fe3+ at the enzyme active site. Indeed, similar to the catecholic redox inhibitor nordihydroguaiaretic acid, SA inhibited with the same efficiency both ferric and the native ferrous SLO form, indicating that these compounds reduce the active ferric enzyme leading to its inactivation.


CONCLUSIONS
SA can inhibit lipoxygenase-catalyzed lipid peroxidation at therapeutic concentrations, suggesting its possible inhibitory activity against enzymatic lipid peroxidation in the clinical setting.
Lapenna
Domenico
D
Dipartimento di Medicina e Scienze dell'Invecchiamento, and Centro di Scienze dell'Invecchiamento-Fondazione Università G. d'Annunzio, Facoltà di Medicina e Chirurgia, 66100 Chieti, Italy. dlapenna@unich.it
Ciofani
Giuliano
G
Pierdomenico
Sante Donato
SD
Neri
Matteo
M
Cuccurullo
Chiara
C
Giamberardino
Maria Adele
MA
Cuccurullo
Franco
F
D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000737:chemistry*; D001092:Arachidonate 12-Lipoxygenase / Q000737:chemistry; D001093:Arachidonate 15-Lipoxygenase / Q000737:chemistry; D001094:Arachidonate 5-Lipoxygenase / Q000737:chemistry; D016718:Arachidonic Acid / Q000737:chemistry; D003864:Depression, Chemical; D004281:Docosahexaenoic Acids / Q000737:chemistry; D005290:Ferric Compounds / Q000737:chemistry; D016166:Free Radical Scavengers / Q000737:chemistry; D006801:Humans; D019787:Linoleic Acid / Q000737:chemistry; D015227:Lipid Peroxidation; D008084:Lipoxygenase / Q000737:chemistry*; D010084:Oxidation-Reduction; D011817:Rabbits; D011994:Recombinant Proteins / Q000737:chemistry; D020156:Salicylic Acid / Q000737:chemistry*; D013025:Glycine max; D013552:Swine
D000894:Anti-Inflammatory Agents, Non-Steroidal; D005290:Ferric Compounds; D016166:Free Radical Scavengers; D011994:Recombinant Proteins; D004281:Docosahexaenoic Acids; D016718:Arachidonic Acid; D019787:Linoleic Acid; D008084:Lipoxygenase; D001092:Arachidonate 12-Lipoxygenase; D001093:Arachidonate 15-Lipoxygenase; D001094:Arachidonate 5-Lipoxygenase; D020156:Salicylic Acid